1. Field of the Invention
The present invention generally relates to a document-sheet conveyance device and an image forming apparatus. Specifically, the present invention relates to a document-sheet conveyance device that reads a document-sheet with conveying the document-sheet, and the image forming apparatus including the document-sheet conveyance device.
2. Description of the Related Art
A broad wide copier that uses a transfer roll paper is known as an image forming apparatus including a document-sheet conveyance device. In the broad wide copier, sheet-thickness of the document-sheet that can be read is, generally, in an extent from 0.035 mm to 1 mm. However, there has been needed to read a more thicker document-sheet having a thickness of 0.035 mm to 10 mm, for example.
There is disclosed a document-sheet conveyance device that can change a gap between a pair of conveyance rollers that pinch a document-sheet therebetween and convey the document-sheet in accordance with the thickness of the document-sheet, for example, in Japanese Patent Application Laid-open No. 2009-143696. The document-sheet conveyance device disclosed in Japanese Patent Application Laid-open No. 2009-143696 includes: a reader that reads a document-sheet; a first conveyance roller and a first driven roller that are provided upstream of the reader in a sheet conveying direction and pinch and convey the document-sheet; a second conveyance roller and a second driven roller that are provided downstream of the reader in the sheet conveying direction and pinch and convey the document; a document-sheet thickness sensor that is provided upstream of the reader in the document-sheet conveying direction and determines a thickness of the document-sheet: a first changing mechanism that changes the gap between the first conveyance roller and the first driven roller based on the thickness of the document-sheet determined by the document-sheet thickness sensor; and a second changing mechanism that changes the gap between the second conveyance roller and the second driven roller based on the thickness of the document-sheet determined by the document-sheet thickness sensor.
In addition, the document-sheet conveyance device disclosed in Japanese Patent Application Laid-open No. 2009-143696 also includes a third changing mechanism that changes a gap between a contact glass plate included in a reading unit and a white plate placed opposite to the contact glass plate based on the thickness of the document-sheet determined by the document-sheet thickness sensor.
In the conventional document-sheet conveyance device, the first and the second changing mechanism are configured to automatically change, using step motors thereof, the gap between the first conveyance roller and the first driven roller, and the gap between the second conveyance roller and the second driven roller, based on the thickness of the document-sheet determined by the document-sheet thickness sensor. The third changing mechanism is also configured to automatically change, using a stepping motor thereof, the gap between the contact glass plate and the white plate opposite to the contact glass plate based on the thickness of the document-sheet determined by the document-sheet thickness sensor. Therefore, the above-mentioned conventional document-sheet conveyance device can read a multi-kind of document-sheets being different in thickness, but due to the mechanism, a cost of the device is increased.
In light of the foregoing, there is a need to provide a low-cost document-sheet conveyance device that reads the multi-kind of document-sheets being different in thickness and an image forming apparatus including the document-sheet conveyance device.